1. Field of the Invention
The present invention relates to a piezoelectric film comprising a piezoelectric layer. The present invention further relates to an ink jet head comprising the piezoelectric film and a method of forming an image by the head, to an angular velocity sensor comprising the piezoelectric film and a method of measuring an angular velocity by the sensor, and to a piezoelectric generating element comprising the piezoelectric film and a method of generating electric power using the element.
2. Description of the Related Art
Perovskite composite oxide [(Bi, Na)1-6Ba6]TiO3 (hereinafter, referred to as “NBT-BT”) has been recently researched and developed as a non-lead (lead-free) ferroelectric material.
Japanese Patent Publication No. Hei 4-60073 and T. Takenaka et al., Japanese Journal of Applied Physics, Vol. 30, No. 9B, (1991), pp. 2236-2239 disclose that a NBT-BT layer has high piezoelectric performance when the NBT-BT layer has a composition around the Morphotropic Phase Boundary (hereinafter, referred to as “MPB”) having a barium molar ratio β(=[Ba/(Bi+Na+Ba)]) of 3-15%.
Japanese Patent Publication No. 4140796 and E. V. Ramana et al., Solid State Sciences, Vol. 12, (2010), pp. 956-962 disclose that (1-α)(Bi,Na,Ba)TiO3-αBiFeO3 where perovskite composite oxide NBT-BT is combined with perovskite composite oxide BiFeO3. The piezoelectric performance of the (1-α)(Bi,Na,Ba)TiO3-αBiFeO3 is maintained even at a solder reflow temperature of 180 degree Celsius.
C. Zhou et al., Journal of Material Science, Vol. 44, (2009), pp. 3833-3840 discloses that (1-α)(Bi,Na,Ba)TiO3-αBiCoO3 where perovskite composite oxide NBT-BT is combined with perovskite composite oxide BiCoO3. The piezoelectric performance of the (1-α)(Bi,Na,Ba)TiO3-αBiCoO3 is maintained even at a solder reflow temperature of 180 degree Celsius.
S-T. Zhang et al., Journal of Applied Physics, Vol. 107, (2010), 114110, 4 pp. discloses that (1-α)(Bi,Na,Ba)TiO3-αBi(Zn0.5Ti0.5)O3 where perovskite composite oxide NBT-BT is combined with perovskite composite oxide Bi(Zn0.5Ti0.5)O3. The piezoelectric performance of the (1-α)(Bi,Na,Ba)TiO3-αBi(Zn0.5Ti0.5)O3 is maintained even at a solder reflow temperature of 180 degree Celsius.
P. Jarupoom et al., Applied Physics Letters, Vol. 99, (2011), 152901 3 pp. discloses that (1-α)(Bi,Na,Ba)TiO3-αBi(Mg0.5Ti0.5)O3 where perovskite composite oxide NBT-BT is combined with perovskite composite oxide Bi(Mg0.5Ti0.5)O3. The piezoelectric performance of the (1-α)(Bi,Na,Ba)TiO3-αBi(Mg0.5Ti0.5)O3 is maintained even at a solder reflow temperature of 180 degree Celsius.
The (1-α) (Bi, Na, Ba) TiO3-αBi(Mg0.5Ti0.5)O3 has been also expected as a non-lead ferroelectric material capable of being used instead of PZT. However, the (1-α) (Bi, Na, Ba) TiO3-αBi(Mg0.5Ti0.5)O3 has a lower piezoelectric performance than the PZT.
A buffer layer can be interposed between a substrate and a piezoelectric film to improve the piezoelectric performance of the piezoelectric film. The buffer layer is referred to as an interface layer. Japanese Patent Laid-Open Publication No. 2007-266346 and Japanese Patent Laid-Open Publication No. 2007-019302 disclose a buffer layer including at least one element contained in the piezoelectric film.
A ferroelectric material containing (Bi, Na, Ba) TiO3, BiFeO3, BiCoO3, Bi(Zn0.5Ti0.5)O3, or Bi(Mg0.5Ti0.5)O3 has high dielectric loss. When the dielectric loss is high, the ferroelectric performance and the piezoelectric performance are decreased significantly.
International Patent Publication WO2010/084711 discloses an NBT-BT layer formed on a LaNiO3 layer.